A Fresnel mirror which is planar and serves as a convex mirror or a concave mirror is known (see, for example, Patent literature 1). On one surface of a substrate of a transparent resin of the Fresnel mirror, a plurality of annular minute grooves are concentrically arrayed. The minute grooves have V-shaped cross-sections and have a surface which is covered with a reflective layer. The Fresnel mirror that serves as the convex mirror is planar, but has an advantage that a wide-angle image is reflected in the mirror, and thus, for example, the Fresnel mirror is attached, in a planar manner, to an internal wall of an overhead bin of a passenger aircraft or the like and is used as the internal check mirror for confirming whether or not any baggage has been left in the overhead bin (see, for example, Patent literature 2).
In some large passenger aircraft, the number of seats ranges from 500 to 800, for each 2 to 3 seats, an overhead bin is provided, and an internal check mirror is provided in the overhead bin. Therefore, the weight of each Fresnel mirror which is attached to the overhead bin is preferably as light as possible in order to reduce a weight load to the passenger aircraft.
A substrate of the Fresnel mirror of a conventional internal check mirror is manufactured through injection molding using a molten resin from the viewpoint of productivity. However, in the injection molding, since the molten resin receives a high flow resistance in a die, a substrate having a thickness of more than about 1.6 mm cannot be molded without causing an unevenness in thickness. Due to the limitation in the thickness and the weight limitation per one mirror described above, an area (vertical dimension×horizontal dimension) of the substrate which can be manufactured through the injection molding is also naturally limited, and the area is limited to 170 mm×170 mm, 150 mm×200 mm and the like.
As described above, to check an entire area of the overhead bin using the internal check mirror which includes the substrate with the limited area, a radius of curvature of a virtual arc of the Fresnel mirror needs to be smaller than 200 mm. This reduces a size of the image reflected in the internal check mirror, and thus, when a piece of baggage in the overhead bin is small, there is a problem that the small baggage is missed.
Further, as another problem, when the thickness of the substrate is large to exceed 1.6 mm, the baggage is caught at the mirror when the baggage is taken in and out, and this results in falling off and a damage of the internal check mirror. Further, when the internal check mirror largely projects from a surface of the internal wall, there is a problem that an appearance is also deteriorated.